My partner of 3 years has gone overseas?

my partner of 3 years has gone overseas to a very good friend of his of 26 years to help him with his business and maybe turn it into a partnership between them, the problem is his wife has been out on he road helping him and not his friend as he's been doing his other job.. before my partner left he had told me that his wife once sleep around on him and i have since found out that the husband has been away for the last 9 days leaving my partner at their home and her with there teenage son..i asked him if anything has happened he has ured me nothing has or nothing well but i keep having a bad feeling about it ..the thought of them two in each others company all day just makes me sick... hes been there for 3 weeks now and was there for 2 weeks last year. i keep asking him if hes any closer on making a decision he keeps telling me he doesn't know,, but tells me its not doing to good we need more work..well ive almost had enough do i give him an ultimatum?